Board-on-chip packages

ABSTRACT

The invention encompasses a board-on-chip package comprising an insulative substrate having circuitry thereon and an opening therethrough. A semiconductive-material-comprising die is adhered to the substrate and electrically connected to the circuitry with a plurality of electrical interconnects extending through the opening. A metal foil is in physical contact with at least a portion of the die. The invention also encompasses a method of forming a plurality of board-on-chip packages. An insulative substrate is provided. Such substrate has a repeating circuitry pattern thereon, and a plurality of openings therethrough. The openings are in a one-to-one correspondence with individual of the repeated circuitry patterns. A plurality of semiconductive-material-comprising dies are adhered to the substrate. Circuitry supported by the dies is electrically connected with the circuitry on the substrate utilizing a plurality of electrical interconnects extending through the openings. A metal foil is joined to the substrate and extended over the plurality of dies. The substrate and metal foil are cut to form singulated die packages comprising a single die, a portion of the substrate having a single repeated pattern of the circuitry, and a portion of the metal foil.

RELATED PATENT DATA

This patent resulted from a continuation application of U.S. patentapplication Ser. No. 10/772,204, which was filed Feb. 3, 2004 now U.S.Pat. No. 6,917,107; which is a continuation application of U.S. patentapplication Ser. No. 09/389,844, which was filed Sep. 2, 1999, and isnow U.S. Pat. No. 6,825,550.

TECHNICAL FIELD

The invention pertains to board-on-chip packages, and to methods offorming board-on-chip packages.

BACKGROUND OF THE INVENTION

A prior art method of forming a board-on-chip package (which can begenerally referred to as a die package) is described with reference toFIGS. 1-5. Referring first to FIG. 1, such illustrates a fragment of anassembly 10 comprising an insulative material substrate 12. Substrate 12can comprise, for example, a circuit board, such as the type known inthe art as FR 4™ (which can be obtained from Sumitomo of Japan), or BCB™(which can be obtained from Toppan of Japan).

Substrate 12 comprises a top surface 13 and slits 19 extendingtherethrough. Circuitry 16 is formed on top of surface 13. Circuitry 16and slits 18 form repeating patterns across top surface 13. Therepeating patterns define separate units 19, 21 and 23, each of whichultimately forms a separate board-on-chip package.

Referring to FIGS. 2-4, an enlarged segment of substrate 12,corresponding to unit 21, is shown in three different views. FIG. 2 is atop view similar to the view of FIG. 1, FIG. 3 is an end view, and FIG.4 is a view along the line 4-4 of FIG. 3. Substrate 12 is inverted inthe view of FIG. 3 relative to the view of FIGS. 1 and 2. Accordingly,surface 13 (referred to as a top surface in referring to FIGS. 1 and 2)is a bottom surface in the view of FIG. 3 In referring to FIG. 3,surface 13 will be referred to as a first surface.

S Substrate 12 comprises a second surface 15 in opposing relationrelative to first surface 13. A semiconductive material-comprising chip(or die) 14 is adhered to surface 15 via a pair of adhesive strips 20.Strips 20 can comprise, for example, tape having a pair of opposingsurfaces 22 and 24, with adhesive being provided on both of suchopposing surfaces. Strips 20 typically comprise insulative material.Wire bonds 28 (only some of which are labeled in FIG. 2) extend fromcircuitry 16 and through slit 18 to electrically connect circuitry 16 tobonding pads 25 (only some of which are labeled in FIG. 2) associatedwith chip 14, and to accordingly electrically connect circuitry 16 withcircuitry (not shown) comprised by chip 14. (The wire bonds and bondingpads are not shown in FIG. 4 for purposes of clarity in theillustration.)

FIG. 5 illustrates further processing of the assembly 10. Specifically,FIG. 5 illustrates units 19 and 21 of FIG. 1 after a first encapsulant40 is provided over wire bonds 28, and a second encapsulant 42 isprovided over chips 14 associated with units 19 and 21. First and secondencapsulants 40 and 42 can comprise the same material and preferablycomprise an insulative material, such as, for example, cured epoxy.

Conductive balls 31 are formed over portions of circuitry 16 (shown inFIGS. 1 and 2) to form a ball grid array over circuitry 16. Such arraycan subsequently be utilized to form a plurality of interconnects fromcircuitry 16 to other circuitry (not shown). Conductive balls 31 can beformed of, for example, tin, copper or gold.

Substrate 12 is subjected to a singulation process which separates units19 and 21 from one another, and thus forms individual board-on-chippackages from units 19 and 21. The singulation process can include, forexample, cutting through encapsulant 42 and substrate 12.

A problem which can be associated with board-on-chip packages is thatthe chip can heat during use. The heating can damage electricalcomponents associated with the chip. It would be desirable to developalternative board-on-chip packages which alleviate such heating.

SUMMARY OF THE INVENTION

In one aspect, the invention encompasses a board-on-chip packagecomprising an insulative substrate having circuitry thereon and anopening therethrough. A semiconductive-material-comprising die isadhered to the substrate and electrically connected to the circuitrywith a plurality of electrical interconnects extending through theopening. A metal foil is in physical contact with at least a portion ofthe die.

In another aspect, the invention encompasses another embodimentboard-on-chip package comprising an insulative substrate havingcircuitry thereon and an opening therethrough. A semiconductive-materialcomprising die is adhered to the substrate and electrically connected tothe circuitry with a plurality of electrical interconnects extendingthrough the opening. The die has a first surface facing the substrateand a second surface in opposing relation to the first surface. The diefurther comprises a sidewall surface extending between the first andsecond surfaces. A thermally conductive material is in physical contactwith at least one of the die first surface, second surface and sidewallsurface. The thermally conductive material has a thermal conductivityunder specified conditions equal to or greater than the conductivity ofelemental copper under the same specified conditions.

In yet another aspect, the invention encompasses a method of forming aplurality of board-on-chip packages. An insulative substrate isprovided. Such substrate has a repeating circuitry pattern thereon, anda plurality of openings therethrough. The openings are in a one-to-onecorrespondence with individual of the repeated circuitry patterns. Aplurality of semiconductive-material-comprising dies are adhered to thesubstrate. Circuitry supported by the dies is electrically connectedwith the circuitry on the substrate utilizing a plurality of electricalinterconnects extending through the openings. A metal foil is joined tothe substrate and extended over the plurality of dies. The substrate andmetal foil are cut to form singulated die packages comprising a singledie, a portion of the substrate having a single repeated pattern of thecircuitry, and a portion of the metal foil.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic, fragmentary view of a prior art semiconductorassembly at a preliminary step of a die package forming process.

FIG. 2 is an expanded view of a portion of the FIG. 1 assembly.

FIG. 3 is a cross-sectional view along the line 3-3 of FIG. 2.

FIG. 4 is a cross-sectional view along the line 4-4 of FIG. 3.

FIG. 5 is a view of a portion of the FIG. 1 assembly shown beingsubjected to prior art processing subsequent to that of FIGS. 1-3.

FIG. 6 is a diagrammatic, cross-sectional view of a semiconductorassembly encompassed by the present invention.

FIG. 7 is a top view of the FIG. 6 structure.

FIG. 8 is a diagrammatic, cross-sectional view of a second embodimentsemiconductor assembly encompassed by the present invention.

FIG. 9 is a diagrammatic, cross-sectional view of a third embodimentsemiconductor assembly encompassed by the present invention.

FIG. 10 is a diagrammatic, cross-sectional view of a fourth embodimentsemiconductor assembly encompassed by the present invention.

FIG. 11 is a diagrammatic, cross-sectional view of a fifth embodimentsemiconductor assembly encompassed by the present invention.

FIG. 12 is a diagrammatic, cross-sectional view of a sixth embodimentsemiconductor assembly encompassed by the present invention.

FIG. 13 is a diagrammatic, cross-sectional view of a portion of asemiconductor assembly at a preliminary step of a method encompassed bythe present invention.

FIG. 14 is a view of the FIG. 13 assembly portion shown at a processingstep subsequent to that of FIG. 13.

FIG. 15 is a top view of the assembly comprising the FIG. 14 portion.

FIG. 16 is a cross-sectional side view of the FIG. 14 assembly portionshown after singulation of units encompassed by the FIG. 14 assemblyportion.

FIG. 17 is a diagrammatic, cross-sectional view of a semiconductorassembly processed according to another embodiment method of the presentinvention.

FIG. 18 is a view of the FIG. 17 assembly shown at a processing stepsubsequent to that of FIG. 17.

FIG. 19 is a view of a semiconductor assembly formed in accordance withanother method encompassed by the present invention.

FIG. 20 is a view of a semiconductor assembly formed in accordance withyet another embodiment method encompassed by the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

A semiconductor assembly encompassed by the present invention isillustrated as assembly 50 in FIG. 6. Assembly 50 comprises aninsulative substrate 52 having an opening (or slit) 54 extendingtherethrough. Substrate 52 comprises a first surface 56 and a secondsurface 58 in opposing relation to first surface 56. Circuitry (such as,for example, the circuitry 16 described with reference to prior artFIG. 1) can be formed over first surface 56. Substrate 52 canaccordingly comprise a substrate identical to that described assubstrate 12 with reference to FIG. 1 of the prior art. In particularembodiments, substrate 52 can comprise a printed circuit board, such as,for example, either a board of the type known as FR-4 in the art, or ofthe type known as BCB in the art.

Conductive balls 60 are formed over first surface 56 of substrate 52,and can comprise, for example, materials of the type described for priorart conductive balls 31 with reference to FIG. 5.

A semiconductive-material-comprising die (or chip) 62 is adhered tosecond surface 58 of substrate 52. Chip 62 comprises a first surface 64aligned to face toward second surface 58 of substrate 52. Chip 62further comprises a second surface 66 aligned to face away from secondsurface 58 of substrate 52. Additionally, chip 62 comprises a firstsidewall surface 68 and a second sidewall surface 70 in opposingrelation to first sidewall surface 68, with sidewall surfaces 68 and 70extending between the surfaces 64 and 66. Chip 62 can comprise aconstruction identical to that described above for chip 14 of the priorart.

Electrical interconnects 72 extend from chip 62, through opening 54, andto the circuitry (not shown) on first surface 56 of substrate 52.Interconnects 72 can comprise wire bonds identical to the wire bonds 28described above with reference to prior art FIGS. 1-5.

An encapsulant 74 is formed over electrical interconnects 72 and withinopening 54. Encapsulant 74 can comprise materials identical to thosedescribed for encapsulant 40 of the prior art.

A thermally conductive material 80 is formed over substrate 52 and chip62. Material 80 preferably has a thermal conductivity greater than orequal to that of elemental copper (with thermal conductivity beingdefined as the heat (in calories) transmitted per second through a plate1 cm thick by about 1 cm ² utilizing a temperature differential of about1° C., the thermal conductivity of elemental copper being understood tobe about 1 calorie). The thermally conductive material 80 can improvedissipation of heat from chip 62 relative to prior art board-on-chipconstructions, and can thus alleviate problems associated with chipheating.

In preferred embodiments, material 80 is a metal foil or conductiveepoxy in physical contact with at least a portion of chip 62. Material80 can comprise, for example, a metal foil selected from the groupconsisting of copper foil and aluminum foil. Alternatively, material 80can comprise, for example, a silver-filled epoxy. For purposes ofinterpreting this disclosure and the claims that follow, a metal “foil”is to be understood as a metal sheet that is less than or equal to about500 microns thick.

In the shown embodiment, thermally conductive material 80 contactssubstrate 52 at a first location 82 proximate first sidewall 68, and ata second location 84 proximate second sidewall 70. Thermally conductivematerial 80 extends across the first and second sidewalls and oversecond die surface 66, and is separated from first and second sidewalls68 and 70 by gaps 86 and 88, respectively. A material 90 is providedwithin gaps 86 and 88 to adhere thermally conductive material 80 tosubstrate 52. In the shown embodiment, gaps 86 and 88 are predominatelyfilled (actually entirely filled) with thermally conductive material 90.Material 90 can comprise, for example, an epoxy, and preferablycomprises an electrically conductive epoxy (such as, for example, asilver-filled epoxy). A reason for utilizing the electrically conductiveepoxy is that electrically conductive materials are frequently alsothermally conductive and accordingly the electrically conductive epoxycan help to dissociate heat from chip 62. It is to be understood,however, that material 90 can comprise an insulative material, and inparticular embodiments can comprise a gas, such as, for example, air.

It is noted that among the differences of the embodiment of FIG. 6relative to the prior art (such as, for example, the construction shownin FIG. 3) is that tape 20 (FIG. 3) is eliminated in the embodiment ofFIG. 6. Instead, chip 62 is adhered directly to substrate 52. Suchadhering of chip 62 directly to substrate 52 can be accomplished by, forexample, providing and curing an electrically conductive epoxy betweensurface 64 of chip 62 and surface 58 of substrate 52. Of course, tape(such as, for example, that shown in FIG. 3) can also be utilized toadhere chip 62 with substrate 52 in embodiments of the presentinvention.

FIG. 7 shows a top view of assembly 50, and shows that thermallyconductive material 80 contacts an entirety of second surface 66 of die62, with die 62 being illustrated in phantom view beneath thermallyconductive material 80. In the shown configuration, die 62 comprises arectangular outer periphery having four sides (68, 70, 69 and 71), andconductive material 80 extends outwardly beyond the outer periphery ofthe die and contacts substrate 52 (FIG. 6) at locations proximate eachof the four sides.

Referring again to FIG. 6, it is noted that thermally conductivematerial 80 comprises a bend in extending from surface 58 of substrate52 to surface 66 of die 62. Because thermally conductive material 80comprises such bend, it can be advantageous to utilize flexiblematerials, such as, for example, thin thermally conductive foils for thethermally conductive material 80. A preferred thickness of a metal foilutilized for thermally conductive material 80 is from about 100 micronsto about 800 microns, with from about 150 microns to about 400 micronsbeing more preferred. Of course, the invention encompasses embodimentsin which material 80 does not flex, and in such embodiments it can beadvantageous to utilize a material 80 having a thickness greater than800 microns.

A second embodiment assembly of the present invention is described withreference to FIG. 8. In referring to FIG. 8, similar numbering will beutilized as was used above in describing the embodiment of FIG. 6 withthe suffix “a” used to indicate structures shown in FIG. 8.

Referring to FIG. 8, an assembly 50 a comprises an insulative substrate52 a, and a chip 62 a. Chip 62 a comprises sidewalls 68 a and 70 a. Athermally conductive material 80 a is formed over chip 62 a andsubstrate 52 a. The thermally conductive material 80 a of FIG. 8 cancomprise, for example, a metal foil, and can be adhered to substrate 52a and chip 62 a with conductive epoxy provided between the metal foiland surfaces of the chip and substrate.

Assembly 50 a is similar to the assembly 50 of FIG. 6, except that thethermally conductive material 80 a contacts a predominant portion of thesidewalls 68 a and 70 a of chip 62 a, whereas thermally conductivematerial 80 of the FIG. 6 assembly was separated from the predominantportion of chip sidewalls 68 and 70 by gaps 86 and 88. It is noted thatthe sidewalls 68 a and 70 a of FIG. 8 comprise respective lengthscorresponding to the distance between chip surface 64 a and chip surface66 a, and that in the shown embodiment thermally conductive material 80a contacts an entirety of such lengths of sidewalls 68 a and 70 a.

A third embodiment semiconductor assembly encompassed by the presentinvention is described with reference to FIG. 9. In referring to FIG. 9,similar numbering will be utilized as was used above in describing FIG.6, with the suffix “b” used to indicate structures shown in FIG. 9.

FIG. 9 shows an assembly 50 b comprising a substrate 52 b and asemiconductive-material-comprising chip 62 b over substrate 52 b. Chip62 b comprises a first surface 64 b aligned to face substrate 52 b. Chip62 b also comprises a second surface 66 b in opposing relation relativeto first surface 64 b, and accordingly aligned to face away fromsubstrate 52 b. Chip 62 b further comprises opposing sidewalls 68 b and70 b which extend between surfaces 64 b and 66 b.

A first thermally conductive material 80 b extends over chip 62 b andsubstrate 52 b. First thermally conductive material 80 b can compriseidentical constructions as described above for material 80, andaccordingly could comprise, for example, a thin metal foil.

A second thermally conductive material 100 extends over substrate 52 band under chip 62 b. Second thermally conductive material 100 cancomprise an identical construction as first material 80 b, or adifferent construction. In preferred embodiments, thermally conductivematerial 100 and thermally conductive material 80 b will both comprisethin metal foils. In other embodiments, thermally conductive materials100 and 80 b can both comprise, for example, electrically conductiveepoxies, such as, for example, silver filled epoxies.

Thermally conductive material 80 b is separated from sidewalls 68 b and70 b of chip 62 b by gaps 86 b and 88 b. Such gaps can be left void ofconductive materials, or can be filled with a thermally conductivematerial 90 b as shown. Such thermally conductive material can comprise,for example, an electrically conductive epoxy.

A fourth embodiment assembly of the present invention is described withreference to FIG. 10. In referring to FIG. 10, similar numbering will beutilized as was used above in describing the embodiment of FIG. 9, withthe suffix “c” used to indicate structures pertaining to FIG. 10.

FIG. 10 shows an assembly 50 c comprising a chip 62 c, a substrate 52 c,a first thermally conductive material 100 c and a second thermallyconductive material 80 c. The assembly of FIG. 10 is similar to theassembly of FIG. 9 except that thermally conductive material 80 ccontacts a predominant portion of the sidewalls of chip 62 c, whereasthe thermally conductive material 80 b of FIG. 9 was spaced from apredominant portion of the sidewalls of chip 62 b.

A fifth embodiment of the present invention is described with referenceto FIG. 11. In referring to FIG. 11, similar numbering will be used aswas utilized above in describing the embodiment of FIG. 6, with thesuffix “d” used to indicate structures shown in FIG. 11.

An assembly 50 d is illustrated in FIG. 11, and such comprises a chip 62d over a substrate 52 d. Chip 62 d comprises a first surface 64 d facingsubstrate 52 d, and a second surface 66 d in opposing relation relativeto first surface 64 d. A thermally conductive material 80 d extends oversubstrate 52 d and over a portion of chip 62 d. However, in contrast tothe thermally conductive materials of FIGS. 6-10, thermally conductivematerial 80 d contacts only a portion of the second surface 66 d of chip62 d. In the shown embodiment, thermally conductive material 80 d doesnot even cover a predominant portion (i.e., half) of second surface 66d. A prior art encapsulant (such as the encapsulant labeled 42 in FIG.5) can be provided over uncovered portions of substrate 52 d and chip 62d.

A sixth embodiment of the invention is described with reference to FIG.12. In referring to FIG. 12, similar numbering will be utilized as wasused above in describing the embodiment of FIG. 6, with the suffix “e”used to indicate structures shown in FIG. 12.

FIG. 12 illustrates an assembly 50 e comprising an insulative substrate52 e and a semiconductive-material-comprising chip 62 e. Substrate 52 ecomprises a first surface 56 e having circuitry (not shown) formedthereon and a second surface 58 e in opposing relation relative to firstsurface 56 e. A slit 54 e extends through substrate 52 e, and a cavity110 is formed within second surface 58 e and proximate slit 54 e. Chip62 e is received within cavity 110. Chip 62 e comprises a first (orinner) surface 64 e facing substrate 52 e and a second (or outer)surface 66 e in opposing relation relative to first surface 64 e. Athermally conductive material 80 e extends over chip 62 e and substrate52 e. Thermally conductive material 80 e can comprise, for example, ametal foil. It is noted that thermally conductive material 80 e is notflexed over sidewalls of chip 62 e (compare the embodiments of FIGS.6-11). Accordingly, thermally conductive material 80 e can be formed ofrelatively non-flexible materials without adversely affecting processingutilized to form assembly 50 e. Thermally conductive material 80 e canthus comprise a sheet of thermally conductive material having athickness of greater than about 800 microns, as well as comprisingrelatively flexible foils having thicknesses of less than about 800microns. The thermally conductive material utilized for sheet 80 e canbe selected from the group consisting of copper and aluminum. In theshown embodiment, chip 62 e is received entirely within cavity 110 andthermally conductive material 80 e extends over cavity 110 to enclosechip 62 e within the cavity. In other embodiments (not shown) chip 62 ecan have a portion extending outwardly of the cavity.

Chip 62 e and sheet 80 e can be adhered to one another, as well as tosubstrate 52 e utilizing, for example, an electrically conductive epoxy.In the shown embodiment, the sidewalls of chip 62 e are separated fromsubstrate 52 e by gaps 112 and 114. Such gaps can be left open, or canbe filled with a material, such as, for example, a thermally conductivematerial. The thermally conductive material can comprise an electricallyconductive epoxy, such as, for example, silver-filled epoxy.

Referring to FIGS. 13-16, a method of forming an assembly of the presentinvention is described. In referring to FIGS. 13-16, similar numberingwill be used as was utilized above in describing the embodiment of FIG.6, with the suffix “f” used to indicate structures shown in FIGS. 13-16.

Referring first to FIG. 13, a portion of an assembly 200 is illustratedat a preliminary step of the described process. Assembly 200 comprisesan insulative substrate 52 f and a plurality of chips 62 f formed oversubstrate 52 f. Substrate 52 f can comprise, for example, the prior artsubstrate 12 described with reference to FIG. 1.

A plurality of slits 54 f extend through substrate 52 f. Circuitry (notshown) is on a first surface 56 f of substrate 52 f. Such circuitry cancorrespond to, for example, the circuitry 16 of FIG. 1, and accordinglycan be formed in a repeating pattern, with the pattern having aone-to-one correspondence with slits 54 f. Chips 62 f are electricallyconnected with the circuitry on surface 56 f with electricalinterconnects 72 f. Conductive balls 60 f are also associated with thecircuitry on surface 56 f. Encapsulant 74 f is formed over electricalinterconnects 72 f and within gaps 54 f.

A thermally conductive material 80 f (preferably a metal foil) is formedover substrate 52 f and chips 62 f. Metal foil 80 f is adhered to one orboth of substrate 52 f and chips 62 f. Foil 80 f can be adhered by, forexample, utilizing an adhesive to bond foil 80 f to chips 62 f andsubstrate 52 f. An alternate method of adhering foil 80 f to substrate52 f is to melt a portion of foil 80 f together with a portion ofsubstrate 52 f. Such melting can be accomplished by, for example,directing a laser light 210 on the portions which are to be melted. Thelight can heat a localized region of metal foil 80 f together with alocalized region of substrate 52 f. The melted materials of foil 80 fand substrate 52 f can be subsequently cooled to effectively weld foil80 f to substrate 52 f. Although the laser light 210 is shown beingapplied in a direction which impacts foil 80 f instead of substrate 52f, it is to be understood that the laser light could be applied from anopposite direction (i.e., from a direction whereupon the light impingesupon substrate 52 f rather than metal foil 80 f), or from bothdirections simultaneously.

The chips 62 f of assembly 200 are separated from one another by gaps220, and metal foil 80 f extends over gaps 220. Referring to FIG. 14,metal foil 80 f is bent downwardly into gaps 220 to cause foil 80 f tocontact substrate 52 f within gaps 220. In the shown embodiment whereinfoil 80 f is bonded to substrate 52 f prior to being 20 inserted withingaps 220, there is preferably an excess of foil provided between thebonded portions to provide enough material 80 f to accommodate the bendsformed in gaps 220. In alternative embodiments, material 80 f can bebent into gaps 220 before the material is bonded to either substrate 52f or chips 62 f.

After material 80 f is bent into gaps 220, material 80 f is preferablyadhered to substrate 52 f within gaps 220. Such can be accomplished by,for example, utilizing laser light 210 as shown in FIG. 14.Alternatively, such can be accomplished by providing an adhesive oversubstrate 52 within gaps 220 to adhere foil 80 f to substrate 52 f.

FIG. 15 is a top view of the assembly 200 which comprises the portionshown in FIG. 14. Such view shows that assembly 200 comprises a squarepanel having 16 repeating patterns (i.e., four repeating patterns oneach side of the square panel). The panel can comprise a size of, forexample, from about 8″×8″ to about 12″×12″, such as, for example, a sizeof about 10″×10″. Chips 62 f are shown in phantom view in FIG. 15. Alsoshown in FIG. 15 are dashed lines 230 corresponding to locations whereinassembly 200 is cut to form singulated die packages (i.e., singulatedboard-on-chip packages). FIG. 15 further shows solid lines 240corresponding to locations wherein thermally conductive material 80 f isadhered to underlying substrate 52 f (FIG. 14).

Referring to FIG. 16, the portion of assembly 200 of FIG. 14 is shownafter such portion is subjected to a cutting process which separatessubstrate 52 f into three singulated assemblies 250, 252 and 254.

The embodiment described with reference to FIGS. 13-16 is merely anexemplary embodiment for forming assemblies of the present invention. Itis to be understood that the invention encompasses other methods offorming such assemblies. For instance, some of the steps shown in FIGS.13-16 can be done in an order other than that described with referenceto FIGS. 13-16. As an example, encapsulant 74 f and wire balls 60 f canbe provided after the bending of metal foil 80 f within gaps 220. Asanother example, metal foil 80 f can be bonded to at least portions ofsubstrate 52 f during or after the cutting described with reference toFIG. 16.

Another method of the present invention is described with reference toFIGS. 17 and 18. In referring to FIGS. 17 and 18, similar numbering willbe utilized as was used above in describing FIG. 6, with the suffix “g”used to indicate structures shown in FIGS. 17 and 18.

FIG. 17 shows an assembly 50 g at an initial step of the method.Assembly 50 g comprises a substrate 52 g having a first surface 56 g anda second surface 58 g in opposing relation relative to surface 56 g.Circuitry (not shown) is formed on surface 56 g. Such circuitry cancomprise, for example, the circuitry 16 described with reference toprior art FIG. 1. A thermally conductive material 80 g is formed oversurface 58 g of substrate 52 g, and can be adhered to substrate 52 gutilizing, for example, a conductive epoxy. Thermally conductivematerial 80 g preferably comprises a flexible material, such as, forexample, a metal foil. Such metal foil can be selected from the groupconsisting of aluminum foil and copper foil.

An opening 54 g extends through thermally conductive material 80 g andsubstrate 52 g. A semiconductive-material-comprising chip 62 g isprovided over thermally conductive material 80 g and across opening 54g. Chip 62 g comprises a first surface 64 g which faces substrate 52 gand a second surface 66 g in opposing relation relative to first surface64 g. Chip 62 g further comprises sidewalls 68 g and 70 g. Chip 62 g canbe adhered to thermally conductive material 80 g utilizing conductiveepoxy. Conductive interconnects 72 g extend through opening 54 g andelectrically connect chip 62 g with the circuitry formed on surface 56 gof substrate 52 g.

Referring to FIG. 18, thermally conductive material 80 g is wrappedaround chip 62 g. In the shown embodiment, thermally conductive material80 g is provided to be of sufficient length such that the conductivematerial overlaps over second surface 66 g of chip 62 g.

FIGS. 19 and 20 illustrate alternative assemblies 50 g which can beformed utilizing thermally conductive material 80 g with differinglengths. Specifically, FIG. 19 illustrates an assembly 50 g whichresults from utilization of a material 80 g having a length such thatthe material forms a butt joint over surface 66 g of chip 62 g. FIG. 20illustrates an embodiment wherein thermally conductive material 80 g isof a length such that the material leaves a portion of surface 66 guncovered. A prior art encapsulant can be formed over the uncoveredportion.

The methods and apparatuses described in FIGS. 17-20 are merelyexemplary methods and apparatuses. The invention, of course, encompassesother methods and apparatuses. For instance, although the thermallyconductive material 80 g is shown formed against and along sidewalls 68g and 70 g of chip 62 g, it is to be understood that gaps analogous tothe gaps 86 and 88 of FIG. 6 could be left between the sidewalls and thethermally conductive material. Also, it is to be understood thatmaterials shown in FIGS. 17 and 18 could be provided after theprocessing of the conductive material 80 g described with reference toFIGS. 17 and 18. For instance, one or more of the encapsulant 74 g,interconnect 72 g, and conductive balls 60 g could be provided after theprocessing of conductive material 80 g of FIGS. 17 and 18, rather thanbefore such processing. Further, although the processing in FIGS. 17-20shows thermally conductive material 80 g initially provided on bothsides of slit 54 g, it is to be understood that the material could beinitially provided on only one side of the slit and wrapped eitherpartially or entirely around surfaces 66 g, 68 g and 70 g of chip 62 g.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A board-on-chip package, comprising: a substrate having circuitrythereon; a die adhered to the substrate and electrically connected tothe circuitry with a plurality of electrical interconnects, the diehaving a first surface facing the substrate, a second surface inopposing relation to the first surface, and a sidewall between the firstand second surfaces; a flexible metallic material adhered to a portionof the die, the flexible metallic material being adhered to thesubstrate proximate the sidewall and extending across the sidewall totouch the second surface; and wherein the sidewall has a length, whereinthe flexible metallic material is spaced from a predominate portion ofthe sidewall length by a gap, and wherein the gap is filled withelectrically conductive epoxy extending from the sidewall to theflexible metallic material.
 2. A board-on-chip package, comprising: asubstrate having circuitry thereon; a die adhered to the substrate andelectrically connected to the circuitry with a plurality of electricalinterconnects, the die having a first surface facing the substrate, asecond surface in opposing relation to the first surface, and a sidewallsurface extending between the first and second surfaces; a thermallyconductive material touching at least two of the die first surface,second surface and sidewall surface; and wherein the thermallyconductive material comprises a silver-containing epoxy.
 3. Theboard-on-chip package of claim 2 wherein the thermally conductivematerial touches the first surface.
 4. The board-on-chip package ofclaim 2 wherein the thermally conductive material touches the secondsurface.
 5. The board-on-chip package of claim 2 wherein the thermallyconductive material touches the sidewall surface.
 6. The board-on-chippackage of claim 2 wherein the thermally conductive material touches thesidewall surface and the second surface.
 7. The board-on-chip package ofclaim 2 wherein the thermally conductive material touches the sidewallsurface and the first surface.
 8. The board-on-chip package of claim 2wherein the thermally conductive material touches the sidewall surface,the first surface and the second surface.